Fuel supply pump



. Aug. 24,1937. w. LINDBERG FUEL SUPPLY PUMP Filed May 14, 1935INVENTOR. l/Wif/l lf #4 [WI 5579 ZQ ,4

ATTORNEY.

Patented Aug. 24, 1937 I UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to a fuel supply pump for internal combustionengines of the type in which liquid fuel under high pressure is injectedinto combustion supporting air through a suitable nozzle whereby it isatomized without the aid of compressed air.

In such engines the quantity of fuel supplied is controlled byregulating the effective stroke of the fuel pump, and especially in thecase of small high speed engines the pump must be capable of meteringvery small quantities of fuel with a high degree of accuracy. Avariation of a small drop in the fuel corresponds to a variation of alarge per cent of any single charge. Also a very slight differencein'the rate of injection corresponds to a large difference in terms ofdegrees of revolution of the crank shaft of the engine.

There has heretofore been considerable difficulty in providing uniformoperation in such engines due to slight irregularities in the fuel.

supply. Slight dripping of the nozzle at the end of injection or asecondary injection, due to surging of the column of liquid fuel in thefuel supply line, after the termination of the main injection, causes anobjectionable after burning which produces irregularities in operationand decreases the overall efficiency.

It is among the objects of the present invention to'provide a fuel pumpwhich will prevent drip at the nozzle, avoid any secondary injection,

fuel supply system constructed in accordance with the present invention;Fig. 2 shows the discharge valve in open position; Fig. 3 shows amodified form of the discharge valve shown in Fig. 2; Fig. 4 shows aconventional form of the same valve.

Referring to Fig. 1, reference numeral l indicates a pump housing havinga central bore 2. A sleeve 3 forming a pump barrel is fitted in bore 2and is provided with ports 4 and 5 forming intake and relief portsrespectively. A plunger 6 is reciprocative in sleeve 3. A dischargevalve l is provided in the upper end of the pump housing which isconnected to a discharge conduit 8 leading to an injection valve 9.

The quantity of fuel supplied by pumps of this type is variedby theopening of the relief passage 5 at variable points in the dischargestroke of the plunger 6. In the instance shown, this is effected in awell known manner by rotation of the plunger 6 through a rack l0coacting' with a pinion H, the rotation of which is transmitted to. thelower end of the plunger by a sleeve l2. A regulating lip l3 adjacentthe end of the piston opens communication between the pump'chamher I!and the relief port 5 at any desired point in the discharge stroke ofthe plunger which point is determined by the angular position of theplunger.

In the normal operation of pumps of this type, the upward movement ofthe plunger 6 closes the ports 4 and 5. The plunger is moving atrelatively high speed by the time the ports are fully closed. A veryabrupt pressure rise occurs in the pump chamber, the discharge valveopens after a slight lag due to its inertia, and upon leaving its seat,if this valve is of a conventional type such as shown in Fig. 4, it isopen toits greatest extent immediately, and a pressure wave istransmitted along the conduit 8. A material time lag occurs in thetransmission of this wave.

between the discharge valve and the injection valve. The impact of thewave upon the injection valve causes the abrupt opening of the latterand the consequent sudden injection of the fuel into the combustionspace of the engine. If the pump discharge valve is heavy in such astructure, it is likely to move against the spring I5 until its inertiaeffect is dissipated, and then rebound to the seat, thus causing aslight interruption in the supply of fuel to the nozzle and a resultingdecrease in the degree of atomization of the fuel. If this inwardmovement of the discharge valve happens to coincide with the opening ofthe spill or relief passage 5, the valve is forced to its seat with suchvelocity that it tends to rebound. This causes a secondary injectioninto the engine due to the fact that the valve head tends to act as animpact plunger. This secondary injection is of course at lower pressurethan the main injection, is less thoroughly atomized and constitutes aslight overcharge. Inasmuch as the quantity of fuel in the line isdecreased to this extent, the next injection is subnormal, thus causingirregularity in the operation of the engine.

To avoid this difliculty, I place the discharge valve seat in adepression having an internal diameter which is slightly larger than thediameter of the valve head. As shown in Figs. 2 and 3, the valve Icoacts with a seat It which is countersunk as indicated at I! in bushingl8. A small clearance is provided between the head and the countersunkportion so that as the valve leaves its seat the opening through whichfuel may flow -from the pump to the conduit 8 is limited to theclearance between the valve head and bushing, full opening not beinattained until the valve head rises sliahtly above the bushina'. Thisresults inamore :radualpressurerise inthecons duit I without throttlin:the iiow when maximum pressure is attained. This action tends toequaliaethe pressureinthepumpchamber i4 and the conduit 0 before thevalve is in its full open position. There is therefore less tendency forthe 10 valve to move so rapidly that its inertia carries it tOO faralainst 8911118 ll, so that a material.

rebound in the clo'sinl direction is avoided. Whenthereliefpassaaelisopenedbythefurther, upward movement of the plunler l,the pressure 15in the pump chamber II is now reduced'far below thepressure in the conduit l. Downward movement of the head of valve 1after the sam'e passesthe top of the bushing ll tends to withting thebore provided for the discharge valve stern. The skirt acts as a pistonto withdraw a small quantity of fuel from the nozzle during'the'downward movement of the valve after com- 35 munication between thepump chamber and discharae conduit has been completely cut oil. Suchconstructions are effective in preventing dribbling at relativelymoderate speeds, but due toincreasedweiahtaremoresubiecttotheinchargestroke of said plunger, said device com-- prising a poppet valve betweensaid chamber and said conduit, said valve seating in a deprelion thewalls of which flare outwardly at a alieht anglefrom said valve when thesame is in closed position. the clearance between said wall and saidvalve head providing a hiahly restricted mm W. momma.

ertla elects described above. and secondary in-

